An apparatus of the aforedescribed general type is disclosed, for example, in German Patent Documents DE 43 23 472 C2 and DE 296 00 417 U1. In such systems in the case of breakage of the fiber strand along the drafting frame or upstream of the drafting frame, the liberated fibers are drawn off by suction and some turns can wind up on the endless belt and accumulate thereon. Such winding up onto the last belt may be induced by the suction applied through the perforations or slit thereof which communicates the suction to the roving.
It has been proposed to provide a cleaning roll adjacent the belt so as to wipe accumulating fibers from the belt surface. Such a wiping roller may have a felt or other pile surface and hence the wiped off fibers can collect on this roller and require a removal or replacement of the roller from time to time.
If the fibers do collect on the compaction belt, the accumulation thereon may damage the drafting frame at the station at which the roving may be supplied and at adjacent stations, can interfere with proper roving feed to the spinning stations and may otherwise be detrimental to the spinning operation. Indeed, it can cause breakage of neighboring spun threads.
The efforts to use a cleaning roller in the manner described have also been fraught with problems since the cleaning roller must be mounted proximal to the belt and frequently the bearing systems for such rollers have been bulky and not readily accommodatable to the spinning frame. Frequent maintenance is also required to clear or replace such cleaning rollers.
Mention may be made, moreover, of German Patent Document 1,760,832 which has a cleaning device in which a cleaning edge is provided along a roller and along a belt for removing collected fiber in conjunction with a drafting frame. This system does not operate fully satisfactorily, although it does provide two or more edges on a common support and hence simplified mounting of the cleaning system.
Another arrangement deserving of mention is that found in German Published Application 1 251 194 wherein weighted strippers are pivotally mounted above the upper drafting members and carry stripping edges which engage the rollers or belts of the drafting frame and are disposed in a suction duct enabling fibers scraped off from the belt or roller to be evacuated away from the stripper.
In the system of DE 17 60 832 A1, the belt stripper engages directly a straight portion of the belt whereas in DE 1 251 194, a stripper rests directly against the belt. As a consequence, while strippers are provided in these systems, not in conjunction with roving compaction device in accordance with the principles described, the stripping systems tend to increase the frictional resistance to belt movement and that has been found to be detrimental to the efficient operation of the drafting frame and a roving spinning machine embodying same.